The invention relates to an integrated semiconductor circuit with function inputs and function outputs, as well as with function units, which supply the function outputs with output signals which they generate as a function of the input signals applied to the function inputs, as well as to a multi-chip module with a plurality of such integrated semiconductor circuits.
Conventional circuits, embodied as integrated circuits, can be used for the realisation of a great variety of different applications. They can process, for example, digital or analogue signals at low or high power; the frequency of the signals to be processed being in the audio or even in the high frequency range. For the purpose of optimising the integrated circuit to suit the intended application, different technologies are applied in their manufacture. These technologies are so different from each other that it is only possible to a limited extent to integrate the function units assigned to these different application ranges on one single semiconductor chip. It is therefore normal practice to produce every one of the integrated semiconductor circuits by using the technology most suited to the intended application, and then to arrange a plurality of such integrated circuits within a multi-chip module, on a common substrate, where they are then interconnected by using conventional procedures. The multi-chip module is a selfcontained unit, with module inputs and module outputs, that has to be tested for full functionality once the manufacturing process is complete. It is, of course, possible to test the functionality of the individual integrated semiconductor circuits before they are attached to the common substrate, but this does not ensure that they remain fully functional after they have been attached to the substrate and after the connections with the other semiconductor circuits have been established.
As well as the individual integrated semiconductor circuits themselves, also the connections in the multi-chip module on the common substrate can be faulty, making it necessary to create the means to check both the individual integrated semiconductor circuits on the substrate, as well as the connections between the semiconductor circuits for faults.
The invention rests on the requirement of creating an integrated semiconductor circuit of the type indicated above which, when used in conjunction with further similar integrated semiconductor circuits within a multi-chip module, enables all required tests on both the individual integrated semiconductor circuits as well as their interconnections to be carried out.
According to the invention, this requirement is met in an integrated semiconductor circuit of the type indicated above in that by means of test inputs and test outputs, as well as an interface unit, which is inserted between the function units on the one hand, and some of the function inputs and some of the function outputs on the other hand and, by means of test control signals applied to it, can be switched over that it connects these several function inputs to the test outputs or to the function units, and these several function outputs to the test inputs or to the function units.
A multi-chip module with several integrated semiconductor circuits, according to the invention, on a common substrate with a plurality of module outputs, module inputs, module test inputs and module test outputs is characterised in that at least some of the function inputs of at least one integrated semiconductor circuit are connected to at least some function outputs of at least one further integrated semiconductor circuit integrated semiconductor circuit, that at least some of the function outputs of at least one integrated semiconductor circuit are connected to at least some function inputs of at least one further integrated semiconductor circuit, that the test inputs and the test outputs of the integrated semiconductor circuits are connected to the module test inputs or to the module test outputs, respectively, and that the test control signals can be applied to the interface units of the integrated semiconductor circuits by means of additional test control inputs.
The interface unit provided in the integrated semiconductor circuit makes it possible, in a first switching state determined by the test control signal, to allow the integrated semiconductor circuit to operate in its normal mode in that it processes the input signals, which it receives at its inputs, in the function units, and then again outputs the corresponding output signals at its function outputs. In the second switching state of the interface unit, the function outputs and the function inputs are disconnected from the corresponding terminals of the function units, and are connected to test inputs or test outputs, respectively. On account of this switch-over capability of the interface unit, the integrated semiconductor circuit, in this state of the interface unit, can be used as input/output interface unit for a similarly embodied integrated semiconductor circuit within a multi-chip module, that is to be tested. Test input signals can therefore be applied to each further integrated semiconductor circuit via this input/output interface, which are then processed in their function units, and can be output and tested via the test outputs of the semiconductor circuit which in this case only acts as an input/output interface. Because of the particular embodiment of the integrated semiconductor circuits, it becomes therefore possible to test such circuits individually within a multi-chip module.